Fuel injection system for an internal-combustion engine

Abstract

A fuel injection system for an internal-combustion diesel engine has a fuel injector, typically one of several, supplied by way of a high-pressure fuel line with highly pressurized fuel for the injection of the fuel into the combustion space of the internal-combustion engine during an injection operation. A pressure control valve connected in front of the fuel injector in the high-pressure fuel line is provided for controlling the pressure of the fuel injected during the injection operation. The pressure control valve contains a freely displaceable piston operating on both sides and a slide connected into the flow path of the high-pressure fuel line for the opening and closing of the passage cross-section of the flow path of the high-pressure fuel line as a function of the position of the piston. On the forward side of the piston, a first pressure space is provided which acts upon the piston in the opening direction of the slide, and, on the rearward side of the piston, a second pressure space is provided which acts upon the piston in the closing direction of the slide. An adjusting valve is used for adjusting the pressures in the first and/or second pressure space in the sense of a displacement of the piston in the opening or closing position. The fuel injection system according to the invention permits a proportional controlling of the fuel injection pressure during the injection operation over a wide adjusting range.

What is claimed is:  
     
       1. Fuel injection system for an internal-combustion diesel engine, having a fuel injector which is supplied with highly pressurized fuel by way of a common rail high-pressure fuel line for injecting the fuel into the combustion space of the internal-combustion engine during an injection operation, and having a pressure control valve connected in the high-pressure fuel line in front of the fuel injector and downstream of a common rail pressure accumulator for controlling the pressure of the fuel injected during the injection operation, 
       wherein the pressure control valve contains a freely displaceable piston operating on both sides and a slide connected into the flow path of the high-pressure control line for opening and closing the passage cross-section of the flow path of the high-pressure fuel line as a function of the position of the piston, a first pressure space on a forward side of the piston which acts upon the piston in the opening direction of the slide, and a second pressure space on a rearward side of the piston which acts upon the piston in the closing direction of the slide, and  
       wherein an adjusting valve is provided for adjusting the pressures in the first and/or second pressure space in the sense of a displacement of the piston in the opening or closing direction.  
     
     
       2. Fuel injection system according to  claim 1 , 
       wherein the first pressure space provided on the forward side of the piston is connected with the upstream side of the high-pressure fuel line by way of a first flow connection, and  
       wherein the second pressure space provided on the rearward side of the piston is connected with the downstream side of the high-pressure fuel line by way of a second flow connection.  
     
     
       3. Fuel injection system according to  claim 1 , 
       wherein the adjusting valve is provided for adjusting the pressure of the first pressure space.  
     
     
       4. Fuel injection system according to  claim 2 , 
       wherein the adjusting valve is provided for adjusting the pressure of the first pressure space.  
     
     
       5. Fuel injection system according to  claim 3 , 
       wherein the adjusting valve is provided in a relief line connected to the first pressure space.  
     
     
       6. Fuel injection system according to  claim 4 , 
       wherein the adjusting valve is provided in a relief line connected to the first pressure space.  
     
     
       7. Fuel injection system according to  claim 1 , 
       wherein the adjusting valve comprises a proportional actuating device.  
     
     
       8. Fuel injection system according to  claim 3 , 
       wherein the adjusting valve comprises a proportional actuating device.  
     
     
       9. Fuel injection system according to  claim 5 , 
       wherein the adjusting valve comprises a proportional actuating device.  
     
     
       10. Fuel injection system according to  claim 7 , 
       wherein the proportional actuating device is a piezo actuator.  
     
     
       11. Fuel injection system according to  claim 9 , 
       wherein the proportional actuating device is a piezo actuator.  
     
     
       12. Fuel injection system according to  claim 2 , 
       wherein an inflow throttle is provided in the first flow connection connecting the first pressure space with the upstream side of the high-pressure fuel line.  
     
     
       13. Fuel injection system according to  claim 6 , 
       wherein an inflow throttle is provided in the first flow connection connecting the first pressure space with the upstream side of the high-pressure fuel line.  
     
     
       14. Fuel injection system according to  claim 2 , 
       wherein a damping throttle is provided in the second flow connection which is connected with the downstream side of the high-pressure fuel line.  
     
     
       15. Fuel injection system according to  claim 6 , 
       wherein a damping throttle is provided in the second flow connection which is connected with the downstream side of the high-pressure fuel line.  
     
     
       16. Fuel injection system according to  claim 15 , 
       wherein an inflow throttle is provided in the first flow connection connecting the first pressure space with the upstream side of the high-pressure fuel line.  
     
     
       17. Fuel injection system according to  claim 2 , 
       wherein the second flow connection connecting the second pressure space provided on the rearward side of the piston with the downstream side of the high-pressure fuel line is constructed as a flow duct extending in the piston.  
     
     
       18. Fuel injection system according to  claim 6 , 
       wherein the second flow connection connecting the second pressure space provided on the rearward side of the piston with the downstream side of the high-pressure fuel line is constructed as a flow duct extending in the piston.  
     
     
       19. Fuel injection system according to  claim 2 , 
       wherein the second flow connection connecting the second pressure space provided on the rearward side of the piston with the downstream side of the high-pressure fuel line is constructed as an exterior duct.  
     
     
       20. Fuel injection system according to  claim 6 , 
       wherein the second flow connection connecting the second pressure space provided on the rearward side of the piston with the downstream side of the high-pressure fuel line is constructed as an exterior duct.  
     
     
       21. Fuel injection system according to  claim 1 , 
       wherein the slide is constructed in one piece with the piston, the first and second pressure spaces being provided at the ends of the piston, and the slide being provided in a center region of the piston.  
     
     
       22. Fuel injection system according to  claim 21 , 
       wherein the flow path of the high-pressure fuel line forms a transverse connection through the center region of the piston.  
     
     
       23. Fuel injection system according to  claim 9 , 
       wherein the flow path of the high-pressure fuel line forms a transverse connection through the center region of the piston; and  
       wherein the flow duct forming the second flow connection extends in the longitudinal direction of the piston from the second pressure space to the transverse connection forming the flow path of the high-pressure fuel line.  
     
     
       24. A pressure control valve assembly disposable in a common rail high pressure fuel line to control pressure of fuel injected into a combustion chamber from the high pressure fuel line, said control valve comprising: 
       a freely displaceable piston for controlling movement of a slide which is operable to control a flow cross-section in said high pressure line, first and second pressure spaces containing fluid acting on respective opposite ends of said piston, and  
       an adjusting valve operable to adjust pressure in at least one of said first and second pressure spaces to thereby adjustably displace the piston and slide in respective high pressure line flow cross-section opening and closing directions.  
     
     
       25. A pressure control valve assembly according to  claim 24 , 
       wherein the first pressure space provided on the forward side of the piston is connected with the upstream side of the high-pressure fuel line by way of a first flow connection, and  
       wherein the second pressure space provided on the rearward side of the piston is connected with the downstream side of the high-pressure fuel line by way of a second flow connection.  
     
     
       26. A pressure control valve assembly according to  claim 25 , 
       wherein the adjusting valve comprises a proportional actuating device.  
     
     
       27. A pressure control valve assembly according to  claim 26 , 
       wherein an inflow throttle is provided in the first flow connection connecting the first pressure space with the upstream side of the high-pressure fuel line.  
     
     
       28. A pressure control valve assembly according to  claim 27 , 
       wherein a damping throttle is provided in the second flow connection which is connected with the downstream side of the high-pressure fuel line.